Rubber suspension bushing life

it could be the internal plastic steering rack bushing.

 

Bushings made of rubber would be designed to last about as long as rubber hoses, generally the lifespan expected would be about 15 years, which for most would be the life of the car. The environment they are in will affect the lifespan. Rubber eventually degrades from ozone in the air, and heat does not help so bushings near engine heat will degrade more quickly. Some bushings are subject to a lot of load forces and will wear out from use, not time. Control arm and trailing arm bushings on some cars can wear out in about 50,000kms, especially some of the very heavy performance cars driven hard like eg. modern BMW's.

But unless the bushing has dry rotted, or is crumbling, or mechanically worn out it is not a safety or technical problem to have old bushings. The rubber will have hardened over time, so not as good as new and you may have a stiffer ride, less suspension compliance. But some people spend dollars to get stiffer urethane bushings, to get the same effect as a hardened old rubber bushing!

I suspect many old Ferrari's, garage kept and not exposed to harsh conditions, still have many of their original bushings in place. Probably rides a bit stiffer, maybe a bit less noise isolation, but not likely something that in a Ferrari would be as noticed as in a luxury car.

So the answer to the question is the bushings last until they wear out. I can't imagine your 10 year old bushings with only 10,000kms on them are worn out. Maybe a bit harder from the engine heat in the rear suspension. But would not be the cause of a steering shimmy. Steering shimmy sounds like a wheel bearing, tie rod, ball joint or as the other poster noted the internal plastic bushing in the rack. Sometimes the bearings, tie rods and ball joints show no signs of wear, ie. no looseness, noises or other inspectable signs of deterioration, but can still be the problem. The problem only surfaces under the high loads when actually driving the car.

 

Most rubber compounds, be they in tires, motor mounts, suspension bushings, weatherstrips, etc have somewhat limited lifespan, especially when compared to other "solid" materials in automotive applications and is dependent on many variables, including climate (exposure to cold, heat, sun light, etc), frequency/type of use and storage, etc...

My +/- 40 year experience around cars, 30+ of it professionally, has me convinced that tires, in general, should be replaced in no more than 6 years from the date they were manufactured, not when bought/installed as they could already be several or more years old by then.

IMO, any load carrying and/or safety related rubber bushings or component in running gear, steering, suspension, along with brake hoses, etc are usually due for replacement in 10 years (or less), again from the date of their manufacturing, not when bought or installed, as the "new"/NOS bushings could've been sitting on some warehouse shelf for 10 or more years and already be outside their "best before" date by that time.

Yes, many others feel that one might or should be able to get away with longer replacement intervals, but I've always wondered why would any (exotic ?) car owner be so disrespectful toward their priced possession, let alone their own safety and the safety of those they share the road with ?

 

I've seen plenty of 20, 30, 40+ years old new (NOS) steering/suspension/etc bushings or brake hoses come out of the box/wrapping and being only good for novelty shelf display or trash bin, but definitely not for their intended use.

 

Hi ,

What if it just produces a squeeking sound specially after a long drive . When driven in wet / short distances they dont squeek ? There is no clunk over potholes and humps ? The car is driven once a week and its been on for years ? Should the bushings be replaced ?

 

I absolutely agree on the brake lines, and fuel hoses being replaced proactively. But as precious as our exotics are, they remain cars, and the properties of rubber degrading are no different than for a modest car. Replacing some bushings is no small job, and there is simply no need, or safety benefit, to replacing bushings that are not worn or falling apart. You can make the case to replace everything long before the practical service life, but I don't like waste, and replacing things that still have meaningful service life just gives me no pleasure. But of course owning and enjoying a Ferrari need not be rational, so if you feel good doing preventative things of all sorts then I fully get it.

The squeek is probably from the links on the sway bars, front and or rear. The bushings in these are very cheap and easy to replace, the rears especially, and probably degraded from heat, perhaps after the long drive the heat soak is displaying the worn bushing symptom more clearly. When wet the bushing is lubricated so won't squeek. They squeek when they are worn, and clunk when really worn. Try spraying some (rubber safe) silicon spray on the link bushings in the back and see if it goes away. It will be temporary, but will id that as the squeek source. The other bushings on the bar itself could also be worn, if after spraying the link bushings it still squeeks, then spray on the bar bushings as well. Again, very easy to replace if needed, may as well diagnose which ones are worn. Or just proactively replace the bar and link bushings, they are under a lot of load and heat so wear is not unusual. Superformance had these bushings for pretty good prices I recall.

 

Thanks Moysiuan for the reply . Will try your advise .

Luigi

 

Chasing a steering shimmy can make your head spin and they very often come down to the wheels. Even though the tires have been changed and the wheels have been checked for roundness, I would really try and get a hold of a known set of wheels that don't shimmy and try it on the car first. This extra step will ensure you are looking in the correct place and save time and money associated with just changing parts.

Regarding tire and rubber age there is some excellent information on this thread however there are a couple of points I would like to touch on:

1. There is a good amount of research out there particularly by Michelin that demonstrate that there is a HUGE difference between an old NOS tire and a tire that has been through its very first heat cycle. New tires can be stored for well over 10 years with no appreciable loss in performance provided they have not been through a single heat cycle, frozen, or exposed to UV. It is the first heat cycle that truly starts the clock and the subsequent life of the tire has a lot to do with the environment it lived in as opposed to a specific age. As an example a car parked outside in the sun will have a drastically shorter life than a car parked indoors. Given that most of our 'special' cars tend to live pampered lives with limited stresses other than the odd high speed run, tire life of 10-12 years (from the first heat cycle) is much more than safe. Remember that tire life recommendations from manufacturers are very much motivated by covering yourself legally as well as encouraging repeat sales. The same holds true with recommended Ferrari belt services where unfounded fear brought on by the manufacturer is a wonderful motivator for excessive service.

2. I recently replaced EVERY hose on my 1977 308 GTB and carefully inspected all of the hoses. The newest hoses were about 12 years old (all the fuel hoses) while some of the hoses (like the heater hoses and brake booster hose in the rockers) were original to the car; over 40 years old at time of removal. Upon inspection and dissection not a single hose showed signs of cracking or impending failure. While some hoses were certainly stiffer than others, all were pliable and very much could be considered safe despite their age. As a matter of course I replaced all the hoses but my experience was that they were not the 10 year time bomb many people would have you think.

 

412 gt’s have a tendency to “roll “ when turning at a moderate to fast speed. Does the condition of the bushes affect this sideways movement ?


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The condition of bushings can affect high speed cornering as they do locate the suspension and maintain/control the geometry of the wheels. That said the bushing condition (unless diabolically bad) will not affect things as much as the condition of your shocks, springs, and sway bars. The 400/412 are inherently NOT sports cars and will have a lot of body roll due to their height and slow mass transfer. You want to be sure you know what a properly sorted car feels like before judging the performance of your personal car. Lots of times these cars get a bad reputation for this or that because few people ever really experience what they should perform like when everything is well serviced.

 

Thanks , the car has been restored by Russell Reeves formerly marenello and joe macari in England. It just has a totally different ride to my gtc/4 and now I understand as you have explained clearly .

 

If the bushings are visibly supple and have minimal cracking then you should be fine with them.

A shimmy due to a wheel bearing would be incredibly strange especially if they feel ok by spinning them. Wheel bearings will normally howl like crazy before causing any other kind of problem and their condition can, in most instances, be inspected by a simple wheel turn and free play check by just jacking a wheel off the ground and rocking it to feel for play.

Certainly the upper shock bushings could be at fault however I would not ignore the wheels just yet. Some years back I had a Porsche Cayman with a shimmy. Tires were near new and I took it to Porsche where their 'experts' charged me a small fortune to road force balance the tires and told me everything was perfect with the wheels and tires. Problem is that a tire with a fault will still balance and can beat a road force machine and the shimmy was still there. I eventually went to a tiny hole in the wall shop that spun the tire and by eye showed me a tire fault. Michelin warrantied the tire and once replaced the car ran perfect. The difference a really experienced eye made was significant and immediately identified the problem.

John if the wheels are in Toronto I can tell you where I went to to have them looked at. If they are in Dubai do your best to find someone with experience and not just someone at the dealer that knows how to use a tire machine.

 

Was the shimmy there with the old tires? New tire defect rates are actually fairly high, would be great to swap wheels/tires with a known good set and rule that out. I have had a new tire defect once, and batteries fail within a few months, in the battery cases I presumed the problem was everything but the battery and was wrong. So I have learned to revisit the blazingly obvious things first for good reason.

Wheel bearings would not be the first on the list, but since you seem to have done many things, you have to look at the lower probability items, and wheel bearings wobbles can be very hard to diagnose, until you just let it get worse and get obvious noise. The bearing noise can be a quiet hum at speed, which you might not hear in a Ferarri until the wear became much more more severe.

Since you have had suspension work done on the car, might also make sense to go through all the suspension bolts with a torque wrench, and make sure everything is as snug as it is supposed to be. I would not be surprised if something has loosened up, I use locktite medium (blue) on everything as I have had a control arm loosen up once, creating a clunk that was very hard to diagnose, but was just a slightly loose bolt, again the suspension forces are huge and not everything is obvious when inspecting a stationary vehicle.

 

Wheel vibration issues normally show themselves at lower speeds and will generally have a resonance range where if you go faster the vibration stops or changes significantly. If it did it with the old tires then likely that is not the problem.

High speed vibrations are normally due to issues with the dampers or an aero problem. I learned a ton about this the hard way when we developed a violent vibration in a prototype race car last year and did everything shy of replacing the tub to remedy it. In the end the problem was a fault in a shock absorber. In my case the vibration would start almost like a switch at about 160kph but because of the very sensitive nature of the car, was incredibly violent like the wheels were square.

A heavier car like a TR would be much more subtle but once it enters into a suspension resonance it will only get worse with speed. The vibration could start from any corner and would transmit through the steering wheel making it feel like a steering shimmy. A hardened suspension bushing would not do this but a very soft one could. Realistically you would be looking at a weak or dead shock or a broken spring as your potential culprit.

 

Find a shop that has the newest Hunter Road Force Balance machine and a tech that knows how to use it.

Make sure they do everything the machine has to offer: Checking wheel runout, tire runout, ect.

This cured a shimmy on my Jag, which is very picky about tire balance and any runout in the wheels and tires.

They can also place the weights EXACTLY where they are supposed to be: Inboard, outboard or center and can position the tire on the wheel to minimise any road force lumps from a slightly out of round wheel or tire combo.

Cost me $25 per wheel for lifetime balance at the local Goodyear shop. Took 3 tries to get it right, to get the right tech to use everything the HUnter offered and now my Jag rides smooth as silk.
Alden